The present invention relates to the aircraft flight management art and, in particular, to an improved flight management system comprising redundant control display units (CDU's), redundant databuses and a flight management computer (FMC), which automatically responds to detected failures in CDU's or databuses to maintain an operating FMC-CDU interface.
In modern commercial aircraft, a flight crew makes flight plan entries and modifications through a Flight Management System comprising one or more flight management computers (FMC's) and, typically, left and right control display units (CDU's). The FMC's and CDU's are linked by redundant databuses. These CDU's are positioned to be accessed by the pilots for purposes of flight plan data entries into the CDU's and then to the FMC's for implementation of a desired flight plan.
In some aircraft, a third CDU unit has been provided in the flight deck. However, such CDU's are provided to perform functions other than FMC interface. In the event that one of the primary left or right CDU's has failed, this leaves only one CDU remaining for the flight crew to perform FMC operations. Only one operating CDU results in reduced crew capability for dealing with flight management functions even though an additional CDU might be physically on board. Thus, loss of a CDU creates increasing work load for the pilot which has the remaining functional CDU. A second fault in a CDU or associated databus could result in the total loss of CDU control.
In addition, failure of one or more of the redundant databuses can similarly result in reduced system capability.
In certain previous avionics designs, manually operated switches in the cockpit allow the flight crew to reconfigure the data path from the FMC to the CDU's. Given that the switching was simple, there were failure combinations that the crew could not correct, resulting in the loss of one or more CDU's to control the FMC.
In addition, it has not been practical to swap CDU's in flight. Maintenance has to be deferred until completion of the current flight leg.